The invention relates to an electromagnetic actuating device and a camshaft adjustment device with such an electromagnetic actuating device as actuator.
In known electromagnetic actuating devices for adjusting the camshaft, the problem exists that owing to the geometry of the core region and of the armature, due to magnet technology, in the currentless state, an adhesion force acts between the core region of the actuating member of the armature. This adhesion force is intensified by the oil, situated in the adjustment unit, which collects between the contact surfaces of core region and actuating member. The adhesion force which thereby arises acts in particular in the low- and deep temperature range (+10° C. to −40° C.) negatively on the switching times of the electromagnetic adjustment unit. A lengthy idle time of the vehicle can also lead to an intensification of the adhesion force.
In order to reduce the above-mentioned disadvantages, an improved electromagnetic actuating device for adjusting a camshaft in a motor vehicle, described in WO 2008/014996 A1, was developed by the applicant. From the publication, it is known to reduce the adhesion force between the actuating member and the core region, caused by lubricant, in that a slit-shaped recess and/or notch, i.e. depression, is provided in the end face of the actuating member.
The reduction of the contact surfaces between actuating member and core region, proposed by the applicant, involves a distinctly increased surface pressure and hence an increased material stress of the core body of the core region. Attempts exist to improve the wear resistance of the actuating device with, at the same time, a reduced adhesion force. Preferably, at the same time, the efficiency of the actuating device is to be improved.
From DE 20 2007 010 814 U1 and DE 20 2009 001 187 U1 electromagnetic actuating devices are known, which comprise an actuating element which forms an engagement region on the end side and which penetrates a cut-out in permanent magnet means which are arranged on the shell side.
From EP 0 428 728 A1 an electromagnetic actuating device is known, which has an actuating element without permanent magnet means, wherein the actuating device is equipped with a contact element.
DE 20 2007 005 133 U1 and DE 199 00 995 A1 are additionally named with respect to the prior art.